Acrylic polymer, process for the production of the same, biodegradable builder, detergent composition and dispersant

ABSTRACT

An acrylic polymer containing at least one terminal group of general formula (I),                    
     in the molecule and having a number-average molecular weight of 300 to 100,000; and a process for the preparation of the polymer, (where R 1  is hydrogen or methyl; and X 1  is hydrogen, alkali metal or ammonium) The invention provides acrylic polymer free from discoloration, excellent in chelating power, and biodegradable, a builder comprising the polymer, a detergent composition comprising the builder and a surfactant, a dispersant comprising a salt of the polymer, and processes for preparing them efficiently.

TECHNICAL FIELD

The present invention relates to a novel acrylic polymer or oligomer, amethod for producing it, a biodegradable builder comprising the acrylicpolymer or oligomer as a main component, a detergent compositioncontaining the biodegradable builder, and a dispersant. More precisely,the invention relates to a novel acrylic polymer having a specificterminal group, a method for producing it, a biodegradable builder fordetergent comprising the polymer as a main component, a detergentcomposition containing the builder, and a dispersant as prepared byneutralizing the acrylic polymer.

BACKGROUND ART

In general, detergent comprising surfactant as a main component containsa builder as an auxiliary component to the surfactant to thereby improveits detergency. As the builder, known are inorganic compounds which arealkaline in water, and polymers of unsaturated aliphatic carboxylicacids. As examples of the former, mentioned are sodium or potassiumcarbonates, hydrogencarbonates, phosphates, polyphosphates andsilicates, as well as zeolite, etc.; while examples of the latterinclude polyacrylic acid, polymaleic acid, polyitaconic acid, etc.

Of those builders, much used are phosphates, polyphosphates and zeolite,as they are effective, economical and easy to handle. However, these areproblematic from the viewpoint of the protection of the globalenvironment in that phosphates and polyphosphates eutrophicate lakes,marshes and rivers while zeolite precipitates on the ground.

Accordingly, it is desired to develop some other builders of which thecapability (especially, the chelating ability) is, needless-to-say, goodand is at least comparable to that of the conventional builders, whichare biodegradable to be gentle to the environment, without remaining fora long period of time on the earth, and are therefore not problematicfrom the viewpoint of the protection of the global environment, andwhich are economical.

Given that situation, Japanese Patent Application Laid-Open (JP-A) No.Hei-5-239127 discloses chelatable and biodegradable, hydrophiliccrosslinked polymers for builders. To prepare the polymers,water-soluble oligomers, which have little chelatability by themselvesbut contain biodegradable low-molecular components in some degree, arecrosslinked at their main chains with a crosslinking agent, such aspolyethylene glycol, citric acid, tartaric acid or the like, via abiodegradable ester or amido group to thereby increase their molecularweight, and the resulting crosslinked polymers are modified to havechelatability.

However, though having a low molecular weight, the linear polyacrylicacid moiety in those hydrophilic crosslinked polymers is hardlybiodegradable, and, in addition, the polymers contain non-biodegradablehigh-molecular polyacrylic acids to no small extent. Therefore, thebiodegradability of the hydrophilic crosslinked polymers disclosed isnot satisfactory. In addition, the disclosed method for producing thepolymers requires two steps, one for polymerizing the oligomer and theother for crosslinking the polymerized oligomer, and requires thespecial crosslinking agent. Accordingly, desired are chelatable andbiodegradable polymers for builders capable of being produced throughmore simple steps, and a method for producing such polymers.

Of the conventional builders noted above, acrylic polymers such aspolyacrylic acid are specifically noted as being easy to produce throughsimple polymerization and being polycarboxylic acids having goodchelatability. To produce those acrylic polymers, in general, used ishydrogen peroxide as the polymerization initiator (catalyst). Hydrogenperoxide is preferred, as its residue remains little in the polymerformed. However, where acrylic monomers are neutralized with an ordinarybase and then polymerized in the presence of the polymerizationinitiator, hydrogen peroxide, the polymerization efficiency is low. Forthis, proposed was a method of adding a metal such as iron or cobalt, oran amine to the polymerization system. However, the method isproblematic in that the polymers produced are often colored, andtherefore its use is limited. In addition, where acrylic monomers areneutralized with an ordinary base and then polymerized in the presenceof the polymerization initiator, hydrogen peroxide to obtain acrylicoligomers, a large amount of the polymerization initiator, hydrogenperoxide is needed. This is problematic, and the problem must be solved.

In the field of dispersants for inorganic pigments, sodium polyacrylateor the like is used for lowering the viscosity of slurry dispersions andfor improving the viscosity stability thereof. However, polyacrylic acidis not biodegradable as so mentioned above. Also in this field,therefore, it is desired to develop some other dispersants which arebiodegradable without remaining on the earth for a long period of timeand which are economical, like the builders mentioned above.

DISCLOSURE OF THE INVENTION

Given that situation, the object of the present invention is to providea colorless, chelatable, biodegradable and economical acrylic polymer,an efficient method for producing it, a builder which comprises thepolymer and is free from environmental pollution or destruction, adetergent with good detergency comprising the builder and surfactant,and a dispersant for inorganic pigments.

In order to attain the object, we, the present inventors haveassiduously studied, and, as a result, have succeeded in obtaining anacrylic polymer having a specific terminal group (the terminology“acrylic polymer” as referred to herein shall include acrylic oligomersand polymers). We have found that the polymer is colorless, chelatable,biodegradable and economical, and can be produced efficiently in asimple process, that, when a builder comprising the polymer is combinedwith surfactant, an advantageous detergent composition is obtained, andthat an alkali salt of the polymer is useful as a dispersant forinorganic pigments. On the basis of these findings, we have completedthe present invention.

Specifically, the invention provides the following:

(1) An acrylic polymer having, in the molecule, at least one terminalgroup of a general formula (I):

wherein R¹ represents a hydrogen atom, or a methyl group; and X¹represents a hydrogen atom, an alkali metal atom, or an ammonium group,and having a number-average molecular weight of from 300 to 100,000.

(2) The acrylic polymer of (1), which has a plurality of ester bonds inthe molecular chain.

(3) The acrylic polymer of (1), which, after having been hydrolyzed, hasa number-average molecular weight of from 100 to 10,000.

(4) The acrylic polymer of (2), which, after having been hydrolyzed, hasa number-average molecular weight of from 100 to 10,000.

(5) An acrylic polymer having at least one terminal group ofHOOC—CH═CH—COO— in the molecule, having a plurality of ester bonds inthe molecular chain, and having a number-average molecular weight offrom 300 to 100,000.

(6) The acrylic polymer of (5), which, after having been hydrolyzed, hasa number-average molecular weight of from 100 to 10,000.

(7) A biodegradable builder comprising an acrylic polymer as a maincomponent which has, in the molecule, at least one terminal group ofX¹OOC—CH═CH—COO— (where X¹ represents a hydrogen atom, an alkali metalatom, or an ammonium group) and has a plurality of ester bonds in themolecular chain and which has a number-average molecular weight of from300 to 100,000.

(8) The biodegradable builder of (7) comprising an acrylic polymer as amain component which, after having been hydrolyzed, has a number-averagemolecular weight of from 100 to 10,000.

(9) A method for producing an acrylic polymer, comprising polymerizingan acrylic monomer in the presence of an initiator of a percarboxylicacid of a general formula (II):

wherein R¹ represents a hydrogen atom, or a methyl group; and X¹represents a hydrogen atom, an alkali metal atom, or an ammonium group.

(10) The method for producing an acrylic polymer of (9), wherein X¹ andR¹ in formula (II) are hydrogen atoms.

(11) A method for producing an acrylic polymer, comprising polymerizingan acrylic monomer in the presence of a reaction product of maleicanhydride and hydrogen peroxide.

(12) A detergent composition comprising from 1 to 40% by weight of atleast one biodegradable builder of (7), from 1 to 40% by weight ofsurfactant, and from 20 to 98% by weight of the remainder comprising anyof enzyme, bleaching agent and inorganic builder.

(13) A detergent composition comprising from 1 to 40% by weight of atleast one biodegradable builder of (8), from 1 to 40% by weight ofsurfactant, and from 20 to 98% by weight of the remainder comprising anyof enzyme, bleaching agent and inorganic builder.

(14) A dispersant as prepared by neutralizing an acrylic polymer, whichhas, in the molecule, at least one terminal group of X¹OOC—CH═CH—COO—(where X¹ represents a hydrogen atom, an alkali metal atom, or anammonium group) and has a plurality of ester bonds in the molecularchain and which has a number-average molecular weight of from 300 to100,000, with an alkali.

(15) The dispersant of (14), which, after having been hydrolyzed, has anumber-average molecular weight of from 100 to 10,000.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a ¹H-NMR chart (in a solvent of heavy methanol) of the acrylicpolymer obtained in Example 1;

FIG. 2 is an IR chart of the acrylic polymer obtained in Example 1; and

FIG. 3 is a ¹H-NMR chart (in a solvent of heavy water) of the acrylicpolymer obtained in Example 1.

BEST MODES OF CARRYING OUT THE INVENTION

The acrylic polymer of the invention is prepared by polymerizing anacrylic monomer such as acrylic acid. This has, in the molecule, atleast one specific terminal group of a general formula (I):

wherein R¹ represents a hydrogen atom, or a methyl group; and X¹represents a hydrogen atom, an alkali metal atom, or an ammonium group,

and has a number-average molecular weight of from 300 to 100,000. Theacrylic polymer has an essential structural unit of the following:

wherein R is a hydrogen atom or a methyl group.

The acrylic polymer of the invention, which has the specific terminalgroup as noted above and has a relatively small number-average molecularweight, has heretofore been unknown and has been disclosed herein forthe first time. This is characterized by its water-solubility andbiodegradability. In addition, like other conventional polycarboxylicacid-based polymers, the polymer of the invention has high chelatabilityto sequester poly-valent metals. Therefore, the polymer of the inventionhas many applications, for example, as a remover for harmful metals,etc., especially as a component of detergent not causing the destructionof the global environment.

If their molecular weight is increased, conventional acrylic polymersmay have increased chelatability, but their biodegradability is loweredwith the increase in their molecular weight. Being different from suchconventional acrylic polymers, the specific acrylic polymer of theinvention has a specific ester bond at its molecular terminal or itsside chain terminal. Because of its specific molecular structure, theacrylic polymer is significantly characterized in that itsbiodegradability is not lowered even though its molecular weight isincreased.

Accordingly, the number-average molecular weight of the acrylic polymerof the invention is most suitably from 300 to 100,000. As opposed tothis, polymers having a number-average molecular weight of smaller than300 are problematic in the chelatability, while those having anumber-average molecular weight of larger than 100,000 are alsoproblematic in the biodegradability, and those polymers could not attainthe object of the invention.

The terminal residue content of the polymer of the invention can bedetermined through ¹H-NMR. Specifically, the ratio of the peak area, b,derived from the protons in —CH═CH— in the terminal group of the polymerto the peak area, a, derived from the protons in the main chain of thepolymer, concretely, the underlined protons in the following

that is, [(b/a)×100(%)], is preferably not smaller than 0.1%, morepreferably from 0.2 to 5.0%.

If the ratio is smaller than 0.1 9, the terminal residue content of thepolymer relative to the main chain thereof shall be small, or that is,the molecular weight of the polymer of which the ester group has beencleaved is to be too large, resulting in that the polymer could not bebiodegradable.

For example, where the terminal group of the polymer is a maleic acidresidue, the terminal residue content of the polymer may be obtained interms of the ratio of the peak area, b, derived from the protons in—CH═CH— in the terminal maleic acid residue at from 6.3 to 6.6 ppm (withexcepting the peak area for non-reacted maleic acid) to the peak area,a, derived from the protons in the main chain of the polymer such asthose noted above at from 1.0 to 3.6 ppm, or that is, in terms of[(b/a)×100(%)].

In one preferred embodiment of the acrylic polymer of the presentinvention, the polymer has, after having been hydrolyzed under thecondition mentioned hereinunder, a number-average molecular weight offrom 100 to 10,000. The polymer of this preferred embodiment may beprepared according to the method that will be mentioned hereinunder, andits structure may be represented by the general formula (III) mentionedbelow, in which low-molecular acrylic polymer moieties each having anumber-average molecular weight of from 100 to 10,000 are bonded to eachother via an ester bond. In the polymer of that type, it is believedthat the ester bonds may act to improve the biodegradability of thepolymer.

The presence of those ester bonds can be confirmed through ¹H-NMR thatindicates the peak area as derived from the protons in —COO—CH₂— at from4.3 to 4.7 ppm.

The acrylic polymer of the invention generally has a terminal group of—OH, which can be confirmed through ¹H-NMR that indicates —CH₂OH or—CH(OH)COOH. For the terminal OH content of the polymer, it is desirablethat the ratio of the sum, c, of the peak area as derived from theunderlined protons in —CH₂OH at from 3.80 to 3.90 ppm and the peak areaas derived from the underlined proton in —CH(OH)COOH at from 3.94 to4.10 ppm, to the peak area, b, derived from the protons in —CH═CH— inthe terminal group of the polymer, or that is, [(c/b)×100(%)] is notsmaller than 50%, more preferably from 100 to 300%.

If the ratio is smaller than 50%, the number of the specific terminalgroups is small in the polymer that grows while starting from thespecific terminal group, or that is, the number of low-molecular acrylicpolymer units to be bonded to each other via an ester bond to give theintended grown polymer is small, resulting in that the grown polymercould not have the intended degree of biodegradability.

wherein R¹ and X¹ have the same meanings as above;

R² and R³ each independently represent an alkyl group having from 1 to 8carbon atoms, a hydrogen atom, or —OH;

i, j and k each represent an integer of from 0 to 1400.

In the preferred embodiment of the invention, the acrylic polymer has,after having been hydrolyzed, a number-average molecular weight of from100 to 10,000, more preferably from 100 to 5,000, even more preferablyfrom 100 to 2,500. Polymers having a number-average molecular weight oflarger than 10,000, after having been hydrolyzed, will have poorbiodegradability.

In a more preferred embodiment of the invention, the acrylic polymer hasa terminal group of HOOC—CH═CH—COO—. The acrylic polymer of thisembodiment has higher biodegradability.

As acrylic monomers to produce the acrylic polymer of the invention,preferably used are maleic anhydride, maleic acid, fumaric acid and thelike for the monomers to give the terminal group of the polymer. As thecomonomers to be copolymerized with those, preferred are acrylic acid,methacrylic acid, maleic acid, etc.

The acrylic monomers, maleic anhydride and others that form the terminalgroup of the acrylic polymer of the invention may be homo-polymerized togive homopolymers, or may be copolymerized with comonomers of acrylicacid, methacrylic acid and the like to give copolymers composed of twoor more different acrylic monomer units. In the latter, copolymerscomposed of two or more different monomer units, the ratio of thosemonomer units may be freely determined, depending on the ratio of themonomers to be copolymerized.

One preferred combination to give the acrylic polymer of the inventionis comprised of from 25 to 75 mol % of maleic anhydride or maleic acidand from 25 to 75 mol % of acrylic acid and/or methacrylic acid, sincethe acrylic polymer produced from this combination has goodchelatability and biodegradability, and since in the method of producingthe acrylic polymer from this combination, the necessary percarboxylicacid is formed efficiently and the molecular weight of the polymer beingformed is easy to control. More preferred is a combination comprised offrom 25 to 75 mol % of maleic anhydride and from 25 to 70 mol % ofmaleic acid.

Apart from the structure to be derived from the acrylic monomers notedabove, the acrylic polymer of the invention may further has, in its mainchain or at its terminals, structural units based on polymerizableunsaturated compounds of a general formula (IV):

wherein R⁴ represents a hydrogen atom, a methyl group, —OH, or —COOX¹; Yand Z each represent a hydrogen atom, a chlorine atom, —COOX¹,—SO₃X¹,—OH, —OCOR″, —COR″, —CONH₂, —COOOH, or —CHO; X¹ represents a hydrogenatom, an alkali metal atom (e.g., sodium, potassium, lithium), or anammonium group; and R″ represents an alkyl group having from 1 to 12carbon atoms.

The polymerizable unsaturated compounds include, for example, itaconicacid, crotonic acid, α-hydroxyacrylic acid, vinylsulfonic acid,allylsulfonic acid, vinyltoluenesulfonic acid, and their alkali metalsalts, ammonium salts, esters with alcohols having from 1 to 12 carbonatoms; as well as acrylamide, itaconic anhydride, acrolein, etc.

The acrylic polymer of the invention may contain the structural units ofthose polymerizable unsaturated compounds in an amount of from 1 to 50mol % relative to from 50 to 99 mol % of the acrylic monomer units.

The method for producing the acrylic polymer of the invention ischaracterized by polymerizing an acrylic monomer in the presence of apolymerization initiator of a percarboxylic acid of a general formula(II):

wherein R¹ represents a hydrogen atom, or a methyl group; and X¹represents a hydrogen atom, an alkali metal atom, or an ammonium group.

The percarboxylic acid is preferably formed by reacting an acrylicmonomer capable of giving the percarboxylic acid with hydrogen peroxide.As hydrogen peroxide, generally used is aqueous, 25 to 75 wt. % hydrogenperoxide, but preferred is aqueous, 30 to 70 wt. % hydrogen peroxide.

More preferably, the percarboxylic acid is formed in a method ofreacting an acid anhydride with hydrogen peroxide. In this, where maleicanhydride is used, it is cleaved with hydrogen peroxide. In this,therefore, it is believed that hydrogen peroxide acts as apolymerization initiator. Specifically, it is presumed that thepercarboxylic acid (V) as formed through the cleavage of the anhydridewith hydrogen peroxide may react with an acrylic monomer to give theacrylic polymer of the invention which has the group of formula (I) atits molecular terminal or side chain terminal, according to thefollowing reaction scheme.

wherein;

X² represents a hydrogen atom or

and X² of not hydrogen indicates a branched structure;

R′ represents an alkyl group having from 1 to 8 carbon atoms, andincludes R² and R³;

R² and R³ each independently represent an alkyl group having from 1 to 8carbon atoms, a hydrogen atom, or —OH;

R⁵ represents a hydrogen atom, or —COOH; and m and n each represent aninteger of from 2 to 1400.

Alternatively, in the presence of a reaction product of an acrylicmonomer and hydrogen peroxide, maleic anhydride may be reacted withhydrogen peroxide and then polymerized with an acrylic monomer. In thisprocess, obtained is a mixture of an acrylic polymer having the specificterminal group at its molecular terminal or side chain terminal, and anacrylic polymer not having the specific terminal group.

Naturally, it is believed that the reaction using the specific acidanhydride produces a mixture of an acrylic polymer (VI) having thespecific terminal group and an acrylic polymer (VII) not having it,according to the reaction step mentioned below.

wherein;

X² represents a hydrogen atom or

and X² of not hydrogen indicates a branched structure; R′ represents analkyl group having from 1 to 8 carbon atoms, and includes R² and R³;

R² and R³ each independently represent an alkyl group having from 1 to 8carbon atoms, a hydrogen atom, or —OH;

R⁵ represents a hydrogen atom, or —COOH; and

m, n and p each represent an integer of from 2 to 1400.

For the reaction of maleic anhydride with hydrogen peroxide, preferably,the concentration of the reactants is from 20 to 80% by weight, thetemperature is from 20 to 60° C., and the time is from 1 minute to 5hours.

The acrylic polymer of the invention has a number-average molecularweight of from 300 to 100,000. The number-average molecular weight ofthe polymer is naturally defined, depending on the reaction conditionemployed where hydrogen peroxide is used and an acid anhydride ispreviously reacted with hydrogen peroxide. As having the number-averagemolecular weight falling within the defined range, but preferably from1,000 to 25,000, the acrylic polymer of the invention exhibits itscharacteristics of biodegradability, etc.

In the polymerization methods mentioned above, permaleic acid as formedby the reaction of maleic anhydride with hydrogen peroxide acts as apolymerization initiator for the acrylic monomer. Therefore, as comparedwith conventional methods, hydrogen peroxide is consumed moreefficiently in the methods proposed herein, and remains little in thepolymer formed. In addition, according to the proposed methods, it iseasy to produce colorless acrylic polymers, especially oligomers havinga low molecular weight. The acrylic polymer to be produced in themethods has a number-average molecular weight of from 300 to 100,000 orso, or that is, the molecular weight of the polymer produced therein isnot so high to such a degree that the polymer is not biodegradable.Accordingly, the polymer of the invention is favorably used as abiodegradable builder.

The acrylic polymer for the biodegradable builder of the invention isproduced in various methods mentioned hereinabove. After having beenisolated, or directly without being isolated, the acrylic polymerproduced is used as the biodegradable builder of the invention. In thelatter, the reaction mixture comprising the polymer formed andcontaining the residue and even the decomposates of the polymerizationinitiator and the polymerization catalyst used is directly used as thebiodegradable builder.

The acrylic polymer may be produced from the acrylic acids and acidanhydrides mentioned above, to which may be added polymerizableunsaturated compounds of a general formula (IV):

wherein R⁴, Y and Z have the same meanings as above, while using, as thepolymerization initiator, a combination of an acrylic acid and hydrogenperoxide, or a combination of an acrylic acid, hydrogen peroxide, andsulfuric acid or an organic sulfonic acid, or a combination of maleicanhydride and hydrogen peroxide. In this process, the combination forthe polymerization initiator produces a percarboxylic acid, with whichthe monomers are polymerized in the same manner as in the above to givethe intended acrylic polymer.

As examples of the polymerizable unsaturated compounds of formula (IV),referred to are the same previously mentioned hereinabove.

As has been mentioned hereinabove, maleic anhydride is cleaved withhydrogen peroxide to give permaleic acid, and the resulting permaleicacid, which acts as a polymerization initiator, is reacted with anacrylic monomer and a polymerizable unsaturated compound to give theintended acrylic polymer. Alternatively, in the presence of a reactionproduct of an acrylic monomer and a polymerizable unsaturated compoundwith hydrogen peroxide, maleic anhydride may be reacted with hydrogenperoxide and then polymerized with an acrylic monomer to give theintended acrylic polymer. In the latter, it is believed that a mixtureof an acrylic polymer having the specific terminal group at itsmolecular terminal or side chain terminal and having constitutionalunits derived from the polymerizable unsaturated compound, and anacrylic polymer not having the specific terminal group but havingconstitutional units derived from the polymerizable unsaturated compoundmay be obtained.

The biodegradable builder of the invention that consists essentially ofthe acrylic polymer as obtained in the manner mentioned hereinabove hasgood chelatability and biodegradability, and is favorably used as abuilder for detergent. Combining the builder and surfactant gives abiodegradable detergent composition.

The detergent composition of the invention comprises a builder of theacrylic polymer obtained herein and a surfactant, and has gooddetergency. After having been used, wastes of the detergent compositionare degraded by microorganisms. Any and every surfactant may be in thedetergent composition, including, for example, anionic surfactants,cationic surfactants, nonionic surfactants and ampholytic surfactants.

Regarding the amount of the builder and the surfactant to be in thedetergent composition, it is desirable that the two are in thecomposition each in an amount of from 1 to 40% by weight while theremainder of from 20 to 98% by weight comprises any of enzyme, bleachingagent, inorganic builder (e.g., zeolite, sodium carbonate, etc.) andothers.

The anionic surfactants employable herein include, for example, soap offatty acids, salts of alkyl ether-carboxylic acids, salts of N-acylaminoacids, salts of alkylbenzenesulfonic acids, salts ofalkylnaphthalenesulfonic acids, salts of dialkylsulfosuccinates, saltsof α-olefinsulfonic acids, salts of sulfates with higher alcohols, saltsof alkyl ether-sulfuric acids, salts of polyoxyethylene-alkyl phenylether-sulfuric acids, salts of sulfates with fatty acid alkylolamides,salts of alkyl ether-phosphates, salts of alkylphosphates, etc.

The cationic surfactants include, for example, aliphatic amine salts,aliphatic quaternary ammonium salts, benzalkonium salts, benzetoniumchloride, pyridinium salts, imidazolinium salts, etc.

The nonionic surfactants include, for example, polyoxyethylene alkylethers, polyoxyethylene alkylphenyl ethers,polyoxyethylene-polyoxypropylene block polymers,polyoxyethylene-polyoxypropylene alkyl ethers, polyoxyethylene-glycerinfatty acid esters, polyoxyethylene-castor oil, polyoxyethylene-sorbitanfatty acid esters, polyoxyethylene-sorbitol fatty acid esters,polyethylene glycol-fatty acid esters, fatty acid monoglycerides,polyglycerin-fatty acid esters, sorbitan-fatty acid esters, fatty acidalkanolamides, polyoxyethylene-fatty acid amides,polyoxyethylene-alkylamines, alkylamine oxides, etc.

The ampholytic surfactants include, for example, carboxybetain-typecompounds, salts of aminocarboxylic acids, imidazolinium betain, etc.

Neutralizing the acrylic polymer of the invention with an alkali in anordinary manner gives a polymer of which the main chain is composed ofacrylic monomers and which has a number-average molecular weight of from300 to 100,000. As having a carboxyl group and having the specificstructure noted above, the thus-neutralized polymer is hydrophilic andbiodegradable. Therefore, this is extremely useful as a dispersant forinorganic pigments, such as calcium carbonate and clay, which are usedfor paper coating. To neutralize the acrylic polymer of the invention,preferably used is an aqueous solution of NaOH, KOH or the like.

The dispersant may be used by itself, or may be combined with anadditional component of polyvinyl alcohol or the like within the rangenot interfering with the effect of the invention.

From 0.05 to 2.0 parts by weight of the dispersant may be added to 100parts by weight of an inorganic pigment such as clay, and the resultingmixture may be dispersed in water. The resulting dispersion may have lowviscosity and high fluidity.

As being chelatable, the acrylic polymer of the invention is also usableas a scale. inhibitor in various devises of coolant systems, water pipelines in boilers, etc. As being well biodegradable, wastes of theacrylic polymer of the invention have little influences on theenvironment.

Now, the invention is described in more detail with reference to thefollowing Examples, which, however, are not intended to restrict thescope of the invention.

The number-average molecular weight, the constitutional unit content,the Ca-ion chelatability, the biodegradability, the detergency and thedispersing power of the polymer samples prepared hereinunder weremeasured according to the methods mentioned below.

(1) Number-average Molecular Weight

The number-average molecular weight of each sample was measured throughgel permeation chromatography (GPC), using polyacrylic acid as thestandard substance.

For this, used was a Waters' system, ALC/GPC 150C Model equipped with abuilt-in differential diffractometric detector and a column system ofAsahipak (GSM-700+GS310). The mobile phase was acetonitrile/50 mM sodiumacetate (3/7); the column temperature was 40° C.; the flow rate was 0.7ml/min; and the amount of the sample charged was 200 μl.

(2) Number-Average Molecular Weight after Hydrolysis

0.5 g of a sample, 1.5 g of sodium methoxide, 5 ml of methanol and 10 mlof water were put into a 100-ml flask, and heated at 90° C. for 8 hours.After the reaction, the resulting hydrolysate was freeze-dried, and itsnumber-average molecular weight was measured through GPC in the samemanner as above.

(3) Determination of Molecular Structure through ¹H-NMR

The terminal maleic acid residue content and the terminal OH content ofeach sample, and the presence or absence of ester bonds in each samplewere measured through ¹H-NMR.

For this, used was a JEOL's system, JMN-EX90 Model. A solution of apolymer sample in a solvent of heavy methanol, having a polymerconcentration of smaller than 5%, was put into a test tube having adiameter of 5 mmØ, and analyzed at room temperature in a NON mode at 90MHz, and the data were integrated 32 times (see FIG. 1).

On the other hand, using a system of JEOL Ltd., GSX-400 Model, asolution in heavy water of the polymer sample having a polymerconcentration of smaller than 5% was put into a test tube having adiameter of 5 mmØ, and analyzed at room temperature in an SGNON mode at400 MHz, and the data were integrated 32 times (see FIG. 3).

(4) Ca-ion Chelatability (ability to sequester Ca⁺⁺)

10 mg of a polymer sample was put into a 50-ml beaker, to which wasadded 50 ml of an aqueous solution containing 0.001 mols/liter ofcalcium chloride and 0.08 mols/liter of potassium chloride. These weremixed in a thermostat tank at 25° C., and the divalent Ca-ionconcentration in the aqueous solution was measured using an ion counter.This was converted into the amount of CaCO₃ as trapped by 1 g of thepolymer, which indicates the Ca⁺⁺-sequestering ability (mg·CaCO₃/g) ofthe polymer sample.

(5) Biodegradability

According to JIS K0102-1989, the biochemical oxygen demand (BOD) of eachpolymer sample was obtained from the amount of the dissolved oxygen asconsumed by the sample having been stirred at 25° C. for 30 days. Basedon this, the degree of biodegradation of the sample was obtainedaccording to the following equation.

Degree of Biodegradation (%)=(BOD/TOD)×100

wherein;

BOD is the biochemical oxygen demand of the sample; and

TOD is the theoretical oxygen demand of the sample.

(6) Detergency:

organic soiling components mentioned below, burnt clay and carbon blackwere mixed in a ratio of 69.7/29.8/0.5 (by weight) to prepare anartificial soiling composition.

Oleic Acid 28.3 wt.pts. Triolein 15.6 wt.pts. Cholesterol-olein 12.2wt.pts. Liquid Paraffin 2.5 wt.pts. Squalene 2.5 wt.pts. Cholesterol 1.6wt.pts. Gelatin 7.0 wt.pts. Total 69.7 wt.pts.

Clean fabric was soiled with this artificial soiling composition in anwet system using an aqueous solvent, and the thus-soiled fabric was cutinto pieces of 5 cm×5 cm each. These pieces had a degree of reflectivityof from 38 to 43%. The surface reflectivity of each soiled piece wasmeasured. Those soiled pieces were subjected to a washing test under thecondition mentioned below.

Washing Condition:

Washing Tester: Terg-O-Tometer Number of Revolution: 120 rpm Hardness ofWater: 90 ppm (in terms of CaCO₃) Amount of Washing Liquid: 900 mlWashing Temperature: 30° C. Concentration of Detergent: 0.067% BathRatio: 30 times Washing Time: 10 minutes Rinsing Time: Two times for 3minutes each

Drying: Sandwiched between sheets of filter paper and dried by ironing.

Next, the surface reflectivity of the washed test piece was measured,and the detergency of the detergent tested was obtained according to thefollowing equation.

Detergency (%)=[(K/S of soiled fabric)−(K/S of washed fabric)]/[(K/S ofsoiled fabric−(K/S of clean fabric)]×100

wherein;

K/S=(1−R)²/2R (Kubelka-Munk's equation) in which R indicates the surfacereflectivity of fabric.

(7) Evaluation of Dispersing Power

A slurry comprised of calcium carbonate (manufactured by Kanto ChemicalCo.) and water in a ratio of 60/40 (by weight) was prepared, to whichwas added a sodium salt of a polymer sample in an amount of 0.3% byweight relative to the amount of calcium carbonate in the slurry, andstirred for 3 minutes. After having been left static for 1 minute, theviscosity of the resulting mixture was measured with a B-type rotaryviscometer (Viscometer VT-04 Model, manufactured by RION Co.), whichindicates the dispersing power of the polymer sample tested. Theviscosity measured of the slurry to which no polymer was added was 10dPa·s.

EXAMPLE 1

39.22 g of maleic anhydride and 22.6 g of aqueous, 60% hydrogen peroxidewere put into a 500-ml separable flask equipped with a stirrer and athermocouple, and stirred at 50° C. for 5 minutes to prepare a uniformsolution. To this were added 57.6 g of acrylic acid and 10 g of water,at a temperature not higher than 20° C., and stirred. The resultingsolution was dropwise put into a separable flask being heated in an oilbath at 100° C., with stirring over a period of 1 hour. After thesolution was all put into the flask, it was further stirred under heatfor 2 hours. After the reactants were thus reacted, the amount ofhydrogen peroxide still remaining in the reaction system was measured.The amount of the non-reacted hydrogen peroxide remained in the systemwas 0.8% of the original dose of the compound.

The properties of the polymer obtained herein are shown in Table 1, inwhich are also shown the amount and the yield of the polymer obtained(the same shall apply hereinunder).

FIG. 1 shows the ¹H-NMR chart of the polymer solution in heavy methanol,in which are seen absorption peaks for C═C at 6.3 ppm, for the estermoiety at 4.3 ppm and for the acrylic polymer backbone at from 1.4 to3.1 ppm. FIG. 2 shows the IR chart of the polymer, in which are seenabsorption peaks for the ester moiety at 1740 cm⁻¹, for the carboxylgroup at 1726 cm⁻¹, and for C═C at 1633 cm⁻¹. These data verify that thepolymer obtained herein is polyacrylic acid having maleic acid as bondedto the terminal via an ester bond.

Next, the polymer was dissolved in dimethylformamide, and reprecipitatedin a solution of methylene chloride. The polymer residue was isolatedand dried. The dried polymer was then dissolved in a solvent of heavywater, and the resulting solution was subjected to ¹H-NMR. FIG. 3 showsthe ¹H-NMR chart of the polymer solution. The ratio of the peak area, b,derived from the protons in —CH═CH— in the terminal maleic acid residueat from 6.3 to 6.6 ppm to the peak area, a, derived from the protons inthe main chain of the polymer at from 1.0 to 3.6 ppm, or that is, theratio [(b/a)×100(%)] was found to be 2.1%. The ratio of the sum, c, ofthe peak area as derived from the underlined protons in —CH₂OH at from3.80 to 3.90 ppm and the peak area as derived from the underlined protonin —CH(OH)COOH at from 3.94 to 4.10 ppm, to the peak area, b, derivedfrom the protons in —CH═CH— in the terminal maleic acid residue of thepolymer, or that is, the ratio [(c/b)×100 (%)] was found to be 200%.After having been hydrolyzed in the manner noted above, thenumber-average molecular weight of the polymer was measured through GPCto be 710. The data of the polymer obtained herein are shown in Table 1.

EXAMPLE 2

The same process as in Example 1 was repeated, except that the amount ofacrylic acid used herein was 28.8 g. After the reaction, the amount ofhydrogen peroxide still remained in the reaction system was 0.03%. Anaqueous solution of 20 wt. % sodium hydroxide was added to the polymerto make the polymer have a pH of 9.0. The properties of the polymer areshown in Table 1.

EXAMPLE 3

The same process as in Example 1 was repeated, except that the amount ofacrylic acid used herein was 72.0 g. After the reaction, the amount ofhydrogen peroxide still remained in the reaction system was 0.29%. Theproperties of the polymer obtained herein are shown in Table 1.

EXAMPLE 4

Using the same device as in Example 1, 45.3 g of aqueous, 60% hydrogenperoxide, 57.6 g of acrylic acid and 1 g of concentrated sulfuric acidwere stirred under heat at 30° C. for 2 hours. To this was added 39.2 gof maleic anhydride at room temperature, and stirred for 5 minutes. Theresulting solution was dropwise put into a separable flask being heatedin an oil bath at 100° C., with stirring over a period of 1 hour. Afterthe solution was all put into the flask, it was further stirred underheat for 2 hours. After the reactants were thus reacted, the amount ofhydrogen peroxide still remaining in the reaction system was measured tobe 1.7%. The properties of the polymer obtained herein are shown inTable 1.

EXAMPLE 5

The same process as in Example 1 was repeated, except that the amount ofacrylic acid used herein was 72.0 g and that the amount of water was 200ml. After the reaction, the amount of hydrogen peroxide still remainedin the reaction system was 1.1%. The properties of the polymer obtainedherein are shown in Table 1.

EXAMPLE 6

Using the same device as in Example 1, 39.2 g of maleic anhydride and22.6 g of aqueous, 60% hydrogen peroxide were stirred at 50° C. for 5minutes to prepare a uniform solution, to which were added 216.0 g ofacrylic acid, 45.3 g of aqueous, 50% hydrogen peroxide and 1 g ofconcentrated sulfuric acid at a temperature not higher than 20° C., andstirred. The resulting solution was dropwise put into a separable flaskbeing heated in an oil bath at 100° C., with stirring over a period of 2hours. After the solution was all put into the flask, it was furtherstirred for 2 hours. After the reactants were thus reacted, the amountof hydrogen peroxide still remaining in the reaction system was measuredto be 1.9%. The properties of the polymer obtained herein are shown inTable 1.

COMPARATIVE EXAMPLE 1

Using the same device as in Example 1, 57.6 g of acrylic acid and 22.6 gof aqueous, 60% hydrogen peroxide were mixed. The resulting solution wasdropwise put into a separable flask being heated in an oil bath at 100°C., with stirring over a period of 1 hour. After the solution was allput into the flask, it was further stirred under heat for 2 hours.

After the compounds were thus reacted, the amount of hydrogen peroxidestill remaining in the reaction system was measured. The amount of thenon-reacted hydrogen peroxide remained in the system was 38.8% of theoriginal dose of the compound. The properties of the polymer obtainedherein are shown in Table 1.

TABLE 1 Number- Amount average Ca⁺⁺ of Number- Molecular Se- Bio-Polymer average Weight questering degrad- Formed Yield Molecular afterAbility ability (g) (%) Weight Hydrolysis (mg/g) (%) Example 1 95.9 993400 710 390 48 Example 2 67.3 99 1100 660 380 66 Example 3 107.8 976800 890 420 35 Example 4 92.9 96 8700 840 470 33 Example 5 105.6 9513500 900 440 33 Example 6 247.5 97 21600 1430 490 26 Com- 52.4 91150000 64000 420 0 parative Example 1

EXAMPLE 7

A detergent composition comprising, as a builder, the polymer of Example1 was tested for its detergency. The data obtained are shown in Table 2.

EXAMPLE 8

A detergent composition comprising, as a builder, the polymer of Example2 was tested for its detergency. The data obtained are shown in Table 2.

COMPARATIVE EXAMPLE 2

In the same manner as in Example 7, except that A-type zeolite was usedin place of the “polymer of Example 1”, a detergent composition wasprepared and tested. The data obtained are shown in Table 2.

COMPARATIVE EXAMPLE 3

In the same manner as in Example 8, except that A-type zeolite was usedin place of the “polymer of Example 2”, a detergent composition wasprepared and tested. The data obtained are shown in Table 2.

TABLE 2 Components of Detergent Composition Comparative Comparative (wt.%) Example 7 Example 8 Example 2 Example 3 LAS 25 20 25 20 AS 10 10 1010 Nonionic Surfactant — 5 — 5 Polymer of 20 — — — Example 1 Polymer of— 20 — — Example 2 A-type Zeolite — — 20 20 Sodium Silicate 10 10 10 10PEG 2 2 2 2 Sodium Carbonate 20 15 20 15 Sodium Sulfate — 5 — 5 Waterbalance Total 100 Detergency (%) 59 64 50 52 LAS Sodium linearalkylbenzensulfonate AS Sodium alkylsulfate PEG Polyethylene glycol

EXAMPLE 9

19.6 g of maleic anhydride and 11.3 g of 60% hydrogen peroxide were putinto a flask, and formed into a uniform solution at room temperature.This solution and 14.4 g of acrylic acid were dropwise put into aseparable flask being heated at 100° C., using a chemical pump for each.The two being put into the flask were stirred therein, and after allwere put into the flask, they were still stirred under heat for 2 hours.After having been cooled, the reaction mixture was made to have a pH of10 with sodium hydroxide added thereto. The polymer thus obtained had anumber-average molecular weight of 1200. Through its ¹H-NMR, the polymerwas found to have ester bonds in the molecule.

According to the method (7) mentioned above for measuring the dispersingpower of the polymer, the viscosity of a slurry mixture comprising thesodium salt of the polymer was measured to be 2.8 dPa·s, which is lowerthan the viscosity of the slurry not containing the polymer of being 10dPa·s, and than the viscosity of the slurry of being 3.4 dPa·scontaining sodium polyacrylate having a molecular weight of 30,000. Thissupports the high dispersing power of the polymer obtained herein.

EXAMPLE 10 to 15

In the same manner as in Example 9, sodium salts of the polymersobtained in Examples 1, and 3 to 7 were tested to evaluate theirdispersing power. The data are shown in Table 3.

Comparative Example 4

In the same manner as in Example 9, the sodium salt of the polymerobtained in Comparative Example 1 was tested to evaluate its dispersingpower. The data are shown in Table 3.

TABLE 3 Dispersing Salt of Polymer Tested Power (dPa·s) Example 9Example 9 2.8 Example 10 Na salt of Example 1 3.1 Example 11 Na salt ofExample 3 2.8 Example 12 Na salt of Example 4 2.9 Example 13 Na salt ofExample 5 3.0 Example 14 Na salt of Example 6 2.9 Example 15 Na salt ofExample 7 2.8 Comparative Example 4 Na salt of Comparative 3.9 Example 1

INDUSTRIAL APPLICABILITY

The novel acrylic polymer of the invention is characterized by itsmolecular structure having a specific terminal group and by itsrelatively low molecular weight. The polymerization initiator usedremains little in the polymer. The polymer has good chelatability and isuseful as a biodegradable builder. Adding the polymer to varioussurfactants produces good detergent compositions. The polymer is alsousable as a biodegradable dispersant.

In addition, as the method for producing the polymer is simple, thepolymer is economical.

What is claimed is:
 1. A method for producing an acrylic polymer,comprising polymerizing an acrylic monomer in the presence of aninitiator of a percarboxylic acid of a general formula (II):

wherein R¹ represents a hydrogen atom, or a methyl group; and X¹represents a hydrogen atom.
 2. The method for producing an acrylicpolymer as claimed in claim 1 wherein X¹ and R¹ in formula (II) arehydrogen atoms.
 3. A method for producing an acrylic polymer, comprisingpolymerizing an acrylic monomer in the presence of a reaction product ofmaleic anhydride and hydrogen peroxide.
 4. A biodegradable buildercomprising an acrylic polymer as a main component which has, in themolecule, at least one terminal group of X¹OOC—CH═CH—COO— wherein X¹represents a hydrogen atom, and has a plurality of ester bonds in themolecular chain and which has a number-average molecular weight of from300 to 100,000, wherein said acrylic polymer is produced by polymerizingan acrylic monomer in the presence of an initiator of a percarboxylicacid of a general formula (II):

wherein R¹ represents a hydrogen atom, or a methyl group; and X¹ is asdefined above.
 5. The biodegradable builder as claimed in claim 4,comprising an acrylic polymer as a main component which, after havingbeen hydrolyzed, has a number-average molecular weight of from 100 to10,000.
 6. A detergent composition comprising from 1 to 40% by weight ofat least one biodegradable builder of claim 4, from 1 to 40% by weightof surfactant, and from 20 to 98% by weight of the remainder comprisingany of enzyme, bleaching agent and inorganic builder.
 7. A detergentcomposition comprising from 1 to 40% by weight of at least onebiodegradable builder of claim 5, from 1 to 40% by weight of surfactant,and from 20 to 98% by weight of the remainder comprising any of enzyme,bleaching agent and inorganic builder.
 8. A dispersant as prepared byneutralizing an acrylic polymer with an alkali, said acrylic polymerhaving, in the molecule, at least one terminal group of X¹OOC—CH═CH—COO—wherein X¹ represents a hydrogen atom, having a plurality of ester bondsin the molecular chain and having a number-average molecular weight offrom 300 to 100,000, wherein said acrylic polymer is produced bypolymerizing an acrylic monomer in the presence of an initiator of apercarboxylic acid of a general foimula (II):

wherein R¹ represents a hydrogen atom, or a methyl group; and X¹ is asdefined above.
 9. The dispersant as claimed in claim 8, which, afterhaving been hydrolyzed, has a number-average molecular weight of from100 to 10,000.